Los Angeles, California (CNN) -- Lawyers for Mel Gibson and his ex-girlfriend attended a closed hearing with a Los Angeles family court judge for two hours Thursday morning, but neither Gibson nor Oksana Grigorieva were there.
Court proceedings in the custody dispute over their 8-month-old daughter are conducted "under seal" with reporters kept waiting in the courthouse hallway. The lawyers for each side refused to address reporters' questions as they left the hearing.
Grigorieva has accused Gibson of striking her in the face, while he alleges that she attempted to extort him to keep controversial recordings of their arguments a secret.
Several explosive audio recordings, purportedly between Grigorieva and Gibson, have been released online in recent days.
RadarOnline released another recording Tuesday of a vicious argument said to be between Gibson and Grigorieva, in which the man is accused of striking the woman and the couple's child -- an accusation the man does not deny.
Police in Malibu Hills, California, opened an investigation earlier this month into an alleged domestic violence incident between Gibson and Grigorieva.
Los Angeles County Sheriff's spokesman Steve Whitmore said last week that the recordings "will be part of the investigation" into the alleged domestic violence.
"In Session" correspondents have made several unsuccessful attempts to reach out to Gibson for comment and to verify whether the voice on the tapes is his.
Grigorieva has filed a restraining order against Gibson, said her spokesman, Stephen Jaffe.
Meanwhile, investigators are looking into the extortion allegations against Grigorieva.
"Allegations of extortion have been brought to our attention and we are certainly going to look into it," Whitmore said Wednesday.
Grigorieva's spokesman told CNN Wednesday that she stands by an earlier statement that there is "no credible evidence" of extortion.
A source close to the investigation told CNN that Gibson's lawyer met with Los Angeles County Sheriff's investigators Tuesday to present evidence that Grigorieva, 40, attempted to extort money from Gibson to keep audio recordings secret.
"To specifically address the allegations, my client, Ms. Grigorieva, has repeatedly stated that there is no credible evidence whatsoever of extortion by her, and she stands steadfastly by that statement," Jaffe said.
CNN's Brittany Kaplan contributed to this report.